I have a little bit of a different take on this.If this situation is as you described it that man owed you some courtesy!I understand the circumstances with his needing money for his wifes medical care,but that does not negate having integrity and recognizing someone who has made a significant investment of time and money to make his property the hunting property it has become.He may have had no choice in his mind but to accept the offer made to him to lease his property.BUT what he could have done is this, contacted you first before he committed to them,explained his circumstances to you and told you that he was going to tell the prospective new people that because of the efforts you have made that he felt a responsibility to you and that had to be factored in to his new agreement.Basically having you not lose your ability to hunt the property you enhanced.
People justify lot's of things when money is being waived in their face.I call it integrity of convenience,when it is convenient to have integrity they have it,when it is tested or bought they don't have it.I am not at all insensitive to this older gentlemans plight!It is just my opinion that he could have handled it in a much more honorable way!
If he had explained his circumstances to you I would sincerely doubt that you would have not made it easy for him to save face.Hunting is important but it does not trump the well being of our friends and their families!